MLB

Preview: D-backs at Reds, 9 a.m., FOX Sports Arizona

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CINCINNATI -- The Cincinnati Reds are rebuilding around young pitching, and the mantra the organization has hammered home at all levels of the minor leagues is to throw strikes.

Guys who do that consistently will get an opportunity at the big-league level. Guys who nibble won't.

Right-hander Luis Castillo, who is scheduled to start the finale of a three-game series against the Arizona Diamondbacks on Thursday afternoon at Great American Ball Park, is learning this lesson as well.

After being promoted from Double-A, Castillo seemed reluctant to challenge major league hitters in the zone, leading to eight walks in his first 10 2/3 innings. But, as his confidence grew, so did Castillo's strike-zone command. He has walked six in his past 18 1/3 innings, with 22 strikeouts.

"This kid's jumping from Double-A," Reds manager Bryan Price said. "He had a little bit of trepidation pounding the strike zone. When he gets on the plate and turns those counts from 1-0 to 0-1, he has a chance to really be sensational. He has a presence beyond his experience and years. I expect that will improve."

Castillo is 1-2 with a 3.41 ERA in five starts, twice being the victim of blown saves. On Thursday, he'll have a tall order against an Arizona club that just added slugging outfielder J.D. Martinez in a trade with the Detroit Tigers on Tuesday.

Martinez, however, left his D-backs debut Wednesday with a left-hand contusion after being hit by a pitch. X-rays were negative and his status for Thursday's matinee finale was uncertain.

"Based on what (head trainer) Ken (Crenshaw) and the medical team has said, we feel like we're in pretty good shape," D-backs manager Torey Lovullo said. "We'll see how it feels tomorrow. I took a deep breath. We're very excited to have J.D. here and thankful that it worked out."

Right-hander Taijuan Walker (6-4, 3.61 ERA) will start for Arizona on Thursday. He lost his only career start against the Reds on July 8 after allowing five runs over five innings. Walker is 4-2 with a 2.70 ERA in eight road starts this season. In his last four starts away from Chase Field, Walker is 3-0 with a 2.35 ERA.

The D-backs (54-40) are off to one of the best starts in franchise history. But they've been scuffling a bit recently; they have lost 12 of 16 games, including a season-high five straight before they beat the Reds in the series opener.

Cincinnati (40-54) had dropped five straight since the All-Star break by a combined 46-14 before earning a 4-3, 11-inning win on Wednesday night to set up Thursday's rubber game. The Reds are rebuilding around a very inexperienced pitching staff, and manager Bryan Price, a former pitching coach, challenged their toughness in a brief tirade after Tuesday's loss.

Wednesday's win provided some relief.

"We were pulling out all the stops to win a good ballgame," Price said.